利用高频背景噪声研究蒲江-新津断裂带北段浅层速度结构  

Velocity Structure of the northern section of the Pujiang-Xinjin Fault Zone from high-frequency background noise method

作　　者：祝玉 孙新蕾 徐守浩 ZHU Yu;SUN Xinlei;XU Shouhao(International Research Center for Planetary Science,Chengdu University of Technology,Chengdu 610059,China;Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]成都理工大学行星科学国际研究中心,成都610059 [2]成都理工大学,成都610059

出　　处：《物探化探计算技术》2025年第2期190-199,共10页Computing Techniques For Geophysical and Geochemical Exploration

基　　金：自然科学基金(42074059);中国科学院基金项目(XDB42020304)。

摘　　要：蒲江-新津断裂带是一条纵贯成都盆地内部规模最大的半隐伏断裂带,南段显露地表,北段则完全隐藏地下。该断裂带靠近主城区,引发地震会对城区人员安全和财产造成威胁,然而我们对新津段北向延伸的隐伏断裂的地下结构了解尚不充分。为了研究蒲江-新津断裂带的地下速度结构及具体展布情况,我们于2023年4月至5月在该断裂带北段周边布设了95台短周期地震仪。笔者利用这些台站的地震波数据提取了0.1 s~2 s的瑞利面波信号,然后采用面波频散直接反演法获得了该区域近地表1.2 km以内的三维剪切波速度结构。结合成都市双流区彭镇周边的沉积层厚度分布以及成都市主要地层地震波速数据,笔者认为研究区域较大尺度的低速异常分布为蒲江-新津断裂带北部隐伏段的展布位置,该断裂带穿过双流彭镇西北侧,进而向北东方向继续前进,延伸至温江区南部四友村附近;研究区域较小尺度的低速异常体有可能是一个北东方向的破碎带。笔者研究结果提供了蒲江-新津断裂带北段的三维S波速度结构,为成都市地下空间探测和地质灾害评估提供了基本参考。The Pujiang-Xinjin Fault Zone(PXFZ)is the largest semi-concealed fault zone in the interior of the Chengdu Basin,whose southern segment is exposed at the surface,and the northern segment remains entirely concealed underground.Potential risks exist due to the fault near the main urban area,which may cause enormous casualties and property loss.However,the location and structure of the northern PXFZ remain ambiguous.In order to study the distribution and the underground velocity structure of the PXFZ,we extract Rayleigh surface wave dispersions from 0.1 s~2 s utilizing seismic ambient noise through 95 short-period seismometers in that area(deploy from April to May 2023).We obtain the three-dimensional shear wave velocity structure within 1.2 km of the near surface in this region.Combining the thickness distribution of sedimentary layers around Pengzhen Town,Shuangliu District,Chengdu City,and the seismic wave velocity data of the main strata in Chengdu City.We propose that the larger-scale low-velocity anomalies correspond to the concealed northern section of PXFZ.This fault zone passes through the northwest side of Pengzhen in Shuangliu,then continues northeastward,extending to the vicinity of Siyou Village in the southern part of Wenjiang District,and the smaller-scale low-velocity anomalies may indicate a north-east-oriented fractured zone.The detailed three-dimensional S-wave velocity structure of the northern PXFZ provides a fundamental reference for the subsurface exploration and geological hazard assessments of Chengdu City.

关 键 词：蒲江-新津断裂带 背景噪声成像 相速度 剪切波速度结构 

分 类 号：P631.4[天文地球—地质矿产勘探]